Stranger Things‘ Charlie Heaton took to Instagram this weekend to pen a sweet birthday tribute to girlfriend and onscreen love interest Natalia Dyer.

The actress turned 23 on Saturday. Heaton, also 23, posted what appeared to be an old photo of her smiling while holding a piece of cake, along with a throwback message.

“Happy 21st birthday!” he wrote. “@nattyiceofficial I hope it’s a great one and I’m stoked to be working on this new series with you. I think it’s gonna be great.”

Heaton and Dyer—who unlike her appearance in his photo, now sports blond hair—play Jonathan Byers and Nancy Wheeler on the ’80s-themed supernatural series, whose second season was released on Netflix in October.

In his message to Dyer, Heaton also wrote, “Not feeling too well but I still wanna meet you at piedmont park tonight x.””See you there x,” Dyer replied.

Piedmont Park is located in Atlanta, where parts of Stranger Things were filmed. Heaton, a British citizen, has not been photographed in the United States since he was reportedly detained at Los Angeles International Airport in October and denied entry into the country due to possession of trace amounts of cocaine. He was not arrested and immediately returned to London, reports said.

As a result of the incident, he missed the Stranger Things season two premiere party and was also unable to take part in press events for the series in the U.S.More than a week later, he said in a statement, “My planned travel to the U.S. last week was affected by an issue at U.S. immigration, and I am working to rectify it as soon as possible. I do want to clarify that I was not arrested or charged with a crime, and cooperated fully with the U.S. officials at LAX. I’m sorry to all the fans and my Stranger Things family for missing the premiere. We are all so proud of this season and I would never want this story to negatively impact the show.”

Since then, he and Dyer have reunited a few times in a few cities in Europe. On Saturday, he walked the red carpet alone at GQ’s 2018 Best Dressed Man event in Milan, Italy.